This project will evaluate performance of 24/7 closed-loop in children and adolescents with type 1 diabetes in the laboratory and home settings. Traditionally, insulin is injected according to blood glucose levels measured with a spot glucose meter up to six times a day. However, insulin needs to be more accurately titrated to attain near-normal blood glucose levels and to reduce the risk of low blood glucose levels. This can be achieved by closed-loop insulin delivery. Glucose is measured on a minute-to-minute basis by a continuous glucose monitor. The signal is transmitted wirelessly to a handheld device, which calculates the right amount of insulin for a given glucose level. The information on the insulin rate is then transmitted wirelessly to an insulin pump. Utilising our knowledge and results obtained during testing of overnight closed-loop insulin delivery, we will develop and test a prototype of closed-loop system for 24/7 closed-loop insulin delivery. The clinical work will start by testing a prototype closed-loop system in controlled laboratory settings. Children and adolescents are known to have larger swings in insulin need than adults and laboratory experience is required to establish the feasibility and safety of closed-loop particularly after meals, during exercise, and following missed meal boluses and unannounced meals. We will proceed to testing 24/7 closed-loop insulin delivery at home settings over 30 days and compare with treatment by the continuous subcutaneous insulin infusion. It is anticipated that our results will contribute to the creation of medical, social, and regulatory acceptance of closed-loop control and will pave the way for its commercial exploitation and a widespread use of 24/7 closed-loop system. PUBLIC HEALTH RELEVANCE: Treatment goals for subjects with type 1 diabetes are difficult to achieve due to an increased risk of hypoglycaemia associated with intensive insulin therapy. The overall objective of this project is to evaluate safety, efficacy, and utility of 24/7 closed-loop control with meal announcement in home settings in children and adolescents with type 1 diabetes. This will be preceded by evaluating 24/7 closed-loop control in compliant and non-compliant subjects in clinical research centre settings to collect data supporting regulatory submission for home testing.